According to its first aspect, the present invention relates to a thin-film magnetic head and a process for its production. More particularly, the invention relates to a thin-film magnetic head that is improved in the insulation layer between magnetic core and coil and which has good magnetic recording characteristics and reproduction efficiency. The invention also relates to a process for producing such an improved thin-film magnetic head.
Thin-film magnetic heads are produced by the same techniques as those used to fabricate integrated semiconductor circuits, including film deposition processes such as evaporation and sputtering, photomechanical processes, and lithographic processes such as etching techniques; these processes permit heads of high precision to be mass produced in one operation.
FIGS. 4a-4f show in cross section the steps involved in a process for producing a thin-film magnetic head as taught in Japanese Patent Laid-Open Publication (Kokai) SHO No. 55-84019. Shown by 1 in FIGS. 4a-4f is a substrate; 2 is a substrate protecting film; 3 is a lower magnetic core; 4 is a magnetic gap; 5 is a first insulation layer; 6 is a copper coil; 7 is a second insulation layer; 8 is an upper magnetic core; 9 is an insulating protective film.
The process of producing the thin-film magnetic head shown in FIG. 4a-4f starts with forming the substrate protecting film 2, the lower magnetic core 3 and the magnetic gap 4 on the substrate 1 (FIG. 4a). The magnetic gap 4 is an inorganic insulating sputtered film, typically formed of alumina. On top of the magnetic gap 4 is formed the lower insulation layer 5 by a photolithographic process using a photoresist of the corresponding shape. The photoresist is cured by heating at 200.degree.-250.degree. C. (FIG. 4b). Subsequently, the copper coil 6 is formed and the upper insulation layer 7 is formed with a photoresist by the same method as used in forming the lower insulation layer 5 (FIG. 4c). Subsequently, the upper magnetic core 8 is formed (FIG. 3d). The copper coil 6, the lower magnetic core 4 and the upper magnetic core 10 are formed by patterned plating. Then, the insulating protective layer 9 is deposited and polished (FIG. 4e). Finally, the assembly is lapped until the end of the upper magnetic core becomes exposed (FIG. 4 f).
The above-described process for producing a thin-film magnetic head has an advantage over the process for producing the conventional bulk magnetic head in that magnetic cores and coil windings can be formed in one operation for each substrate.
However, in that process for producing a thin-film magnetic head, the magnetic cores are formed by plating and, hence, the materials that can be used to make the magnetic cores are limited, thus making it impossible to use materials having better magnetic characteristics. In other words, when forming magnetic cores, it is advantageous to deposit films by dry processes such as sputtering that permit materials selection from a broader range than when the plating method is used.
On the other hand, if magnetic cores are formed by a dry film deposition process such as sputtering in accordance with the procedure shown in FIG. 4, cracks will sometimes develop in the photoresist or the thin magnetic films forming the magnetic cores will come off the underlying layers on account of the gas evolved from the resist and this is due to the temperature elevation that takes place when forming those thin films or due to the heat treatment that is optionally performed to improve the magnetic characteristics of the core.
A further problem is associated with the curing of the photoresist by heating. Above 250.degree. C., the photoresist undergoes extensive thermal decomposition and this makes it difficult to perform the optional heat treatment at 250.degree. C. or above.